This invention relates to techniques for unlocking digital content on systems coupled over a network.
The Internet has become a medium for distributing content. Web servers that host websites often make available various types of content in a digital form. While digital some content is available on websites in a text-based digital form, much content is not available in such a form. Some publishers are reluctant to publish books and other content on websites for example. Generally, when content such as books and the like are published in a digital form they are published in a bitmap or PDF type format.
Publishers are understandably concerned about publishing content in digital format, in general, and accessible digital formats in particular, because material published on websites, is easily illegally copied and distributed. In digital format, publishers risk losing control of a copyrighted work. Some publishers avoid making some or all of their content available in digital format, or protect the content to make the content difficult to copy and to access.
Accordingly, publishers might want to protect content to prevent users from being able to view the content, duplicate the content exactly (e.g. by duplicating the entire CD), printing the content (e.g. printing a copy of the book from the CD), and extracting content, such as text or images, and using the extracted content by reformatting the extracted content, or translating the extracted content or incorporating the extracted content into some other form, such as for searching or indexing.
PDF format has an elaborate set of protections that address some of these protection issues. For example, in PDF, printing can be locked, as can be copying of text, or passwords can be used to lock and unlock copying and printing. In some applications, PDF uses “back door” methods that allow screen readers for the blind to access text, via secret passwords that publishers share with the manufacturers of the screen readers.